* rename .stylelintrc to .stylelintrc.json for explicit file type
* add new npm script lint-fix:style
* fix pseudo-element with double colon
* function name should be lower except ignored functions
* support stylelint declaration-block-no-ignored-properties rule
* support sorted CSS properties order for readability and consistency
* autofix order of all styles by lint-fix:style script
* remove double slash comments after selector
* replace .stylelintignore with ignoreFiles in .stylelintrc.json
#### FEATURES
* use `ContentState` instead of `EditorState`, selection events won't trigger
onChange anymore.
* deprecated `Mention.toEditorState`, instead of `Mention.toContentState`,
* `Mention.toEditorState` are compatibled, but have a warnning in console.
#### ISSUES
* `disabled` and `readOnly` props supported.
* fixed controlled mode bug.
* close#5788
* close#5175
* close #https://github.com/react-component/editor-mention/issues/7
* Add new color patterns algorithm
* Add color palettes
* update other colors
* fix gray color
* update more tint/shade to colorPalette
* new font color
* Update doc for new color system
* improve doc style
+ add `getSuggestionContainer` callback function, which allow users modify the
container element of suggestions dropdown.
+ the suggestions dropdown will mount on `document.body` defaultly, instead of
on editor.
+ close#3588
